The present invention generally relates to bodily fluid sampling devices and more specifically, but not exclusively, concerns an integrated lancing test strip with a lancet contained within a sterility sheet.
The acquisition and testing of bodily fluids is useful for many purposes, and continues to grow in importance for use in medical diagnosis and treatment, such as for diabetes, and in other diverse applications. In the medical field, it is desirable for lay operators to perform tests routinely, quickly and reproducibly outside of a laboratory setting, with rapid results and a readout of the resulting test information. Testing can be performed on various bodily fluids, and for certain applications, is particularly related to the testing of blood and/or interstitial fluid. Performing home based testing can be difficult for many patients, especially for patients with limited hand dexterity, such as the elderly or diabetics. For example, diabetics can sometimes experience numbness or tingling in their extremities, such as their hands, which can make self-testing difficult because they are unable to accurately position a test strip to collect the blood sample. In addition, wounds for diabetics tend to heal more slowly, and as a result, there is a desire to make incisions less invasive.
Recently, integrated lancing test strips have been developed in which a test strip is integrated with a lancet so as to form a single disposable unit. While these integrated units have somewhat simplified the collection and testing of fluid samples, there are still a number of issues that need to be resolved before a commercial unit can be implemented. One issue concerns maintaining the sterility of the lancet so as to minimize the risk of infection. In practice, conventional plastic or syringe type caps that are used to maintain the sterility of typical lancets cannot be incorporated with integrated lancing test strips for several reasons, especially for those designs with lancets that are moveable relative to the rest of the test strip. With typical syringe type caps, the cap encapsulates the lancet, and the cap is removed by pulling or twisting the cap off the lancet. However, the removal of the cap from the lancet without destroying or damaging the integrated device is difficult or even practically impossible. Moreover, automatic cap removal with such caps can be difficult. There is a trend to make lancets smaller or thinner so as to make less traumatic or less invasive incisions, which in turn makes self-monitoring less painful as well as promotes healing of the incision. However, due to their thinner nature, lancets are more prone to bending or are susceptible to other damage, especially when protective caps are removed. Further, the pulling or twisting action during cap removal can damage the test strip, like delicate electrodes in electrochemical type test strip, or can even result in the lancet being separated from the test strip.
Integrated devices have been proposed in which the lancet is encapsulated within a sterilized plastic body or a molded plastic plug that encloses one end of a lancet chamber. During lancing, the lancet pierces the body so as to extend from the body and lance the tissue. Such a design is suitable for automated systems because the lancet can be fired without the need to remove a protective cap. Given their bulky and rigid nature, these types of designs are not well suited for magazines, drums, cassettes, cartridges and the like, however. The encapsulating plastic creates a rather large profile, which does not allow a plurality of integrated devices to be packed in a tight package. Due to the somewhat rigid nature of the encapsulating material, the devices are too rigid by themselves for integration into a reel-to-reel type cassette design. Moreover, the injection molding required to manufacture these types of integrated devices can make the devices considerably more expensive as well as more difficult to assemble. Such designs can also limit how small the lancet can be because the lancet has to be rigid enough to still be able to puncture the seal.
Other integrated disposable designs have been proposed in which the entire unit is sealed within a protective packet. However, these designs require the entire disposable unit to be sterilized at the same time, which results in a whole host of difficulties. Unfortunately, sterilization techniques for lancets, such as radiation, adversely affect the chemical enzymes of the test strip. Hence, if left uncompensated, the accuracy of the test strip can be significantly hampered. To compensate for the changes that occur during sterilization, samples from sterilized lots are taken so that an adjustment or calibration value can be calculated for the lot. Before use, the calibration value for the lot is entered, either manually or automatically, into the meter to compensate for lot variations. Moreover, certain desirable sterilization techniques for lancets are impractical when the lancet and test strip are combined together because these techniques tend to damage or even destroy components on the test strip. In addition, undesirable cross contamination can occur between the lancet and the test strip when sealed in the same protective packet. For instance, components of the test strip, such as chemicals, biological components, adhesives and the like, can migrate within the packet onto the lancet, thereby possibly compromising the sterility of the lancet.
Ensuring that a sufficient amount of body fluid is collected during sampling is another issue that needs to be addressed before a viable commercial integrated lancing test strip can be implemented. It is desirable that the integrated device only lightly contacts the skin during fluid sampling. If the integrated device is pressed too hard against the skin, fluid flow from the incision can be blocked, which can occasionally lead to insufficient sample sizes. However, if the test strip is not touching at all, the test strip may be too far away for the blood drop to reach the capillary entrance of the test strip. When an insufficient amount of fluid for testing is collected, usually the integrated device has to be disposed of, and a new one is used to perform the test again. Further complicating this problem is that the elasticity of skin varies from person to person as well as varies between different body parts on the individual, which can create difficulties in locating the test strip. For example, the skin of a child is more elastic than that of the elderly. As a sampling device is pressed against the skin, the more elastic skin of the child tends to bow or pucker to a greater degree than the inelastic skin of the elderly. This variation of skin puckering height between individuals and body locations makes it difficult to design a meter that can accurately position a test strip so as to not contact the skin or only slightly contact the skin so as to not disturb fluid flow, but still be able to contact the drop of fluid from the incision for fluid collection purposes.
Thus, needs remain for further contributions in this area of technology.